//
//  ArrowPolylineRenderer.swift
//  map_mapkit_ios
//
//  Created by 诺诺诺的言 on 2025/7/14.
//

import UIKit
import MapKit
import Combine


class ArrowPolylineRenderer: MKPolylineRenderer {
    // 箭头属性
    var arrowColor: UIColor = .red
    var arrowSize: CGFloat = 8
    var arrowSpacing: CGFloat = 30   // 默认值
    
    // 边框属性
    var borderWidth: CGFloat = 0
    var borderColor: UIColor = .clear
    
    override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
        // 1. 绘制边框
        if borderWidth > 0 {
            context.saveGState()
            // 边框宽度 = 主线条宽度 + 2倍边框宽度（左右各扩展 borderWidth）
            let borderLineWidth = lineWidth + borderWidth * 2
            context.setLineWidth(borderLineWidth)
            context.setStrokeColor(borderColor.cgColor)
            context.setLineCap(lineCap)  // 保持与主线条一致的线帽样式
            context.setLineJoin(lineJoin) // 保持与主线条一致的拐角样式
            // 绘制边框线条
            super.draw(mapRect, zoomScale: zoomScale, in: context)
            context.restoreGState()
        }
        
        // 2. 绘制主轨迹线
        super.draw(mapRect, zoomScale: zoomScale, in: context)
        
        // 3. 绘制箭头（数量减半）
        drawArrows(mapRect: mapRect, zoomScale: zoomScale, in: context)
    }
    
    private func drawArrows(mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
        guard polyline.pointCount >= 2 else { return }
        
        let scaledArrowSize = arrowSize / zoomScale
        let scaledArrowSpacing = arrowSpacing / zoomScale
        
        var distance: CGFloat = 0
        let points = polyline.points()
        
        // 使用stride跳过每隔一个的箭头
        let step = 2 // 跳过间隔
        var arrowIndex = 0
        
        for i in 0..<polyline.pointCount-1 {
            let startPoint = point(for: points[i])
            let endPoint = point(for: points[i+1])
            
            let dx = endPoint.x - startPoint.x
            let dy = endPoint.y - startPoint.y
            let segmentLength = hypot(dx, dy)
            
            guard segmentLength > 2 / zoomScale else { continue }
            
            let arrowCount = Int(floor((distance + segmentLength) / scaledArrowSpacing))
            
            for j in 0..<arrowCount {
                // 只绘制每隔step个箭头
                if arrowIndex % step == 0 {
                    let position = CGFloat(j) * scaledArrowSpacing - distance
                    let ratio = position / segmentLength
                    
                    guard ratio >= 0 && ratio <= 1 else { continue }
                    
                    let arrowPoint = CGPoint(
                        x: startPoint.x + dx * ratio,
                        y: startPoint.y + dy * ratio
                    )
                    
                    let angle = atan2(dy, dx)
                    drawSingleArrow(at: arrowPoint, angle: angle, size: scaledArrowSize, in: context)
                }
                arrowIndex += 1
            }
            
            distance = (distance + segmentLength).truncatingRemainder(dividingBy: scaledArrowSpacing)
        }
    }
    
    private func drawSingleArrow(at point: CGPoint, angle: CGFloat, size: CGFloat, in context: CGContext) {
        context.saveGState()
        context.translateBy(x: point.x, y: point.y)
        context.rotate(by: angle)
        
        let arrowPath = UIBezierPath()
        arrowPath.move(to: CGPoint(x: 3.2, y: 0))
        arrowPath.addLine(to: CGPoint(x: 0, y: 2.6))
        arrowPath.addLine(to: CGPoint(x: -3.2, y: 2.6))
        arrowPath.addLine(to: CGPoint(x: 0, y: 0))
        arrowPath.addLine(to: CGPoint(x: -3.2, y: -2.6))
        arrowPath.addLine(to: CGPoint(x: 0, y: -2.6))
        arrowPath.close()
        
        context.setFillColor(arrowColor.cgColor)
        context.addPath(arrowPath.cgPath)
        context.fillPath()
        context.restoreGState()
    }
}